Polyurethane resins in water-dilutable basecoats having low flash and quick-drying characteristics

ABSTRACT

This invention, therefore, relates to the field of polyurethane coatings for use in automobile basecoat/clearcoat systems. In particular, this invention relates to the discovery that incorporating a long-chain carboxylic acid of at least 50% by weight of the carboxylic acid component used to make polyester resins which are further incorporated into polyurethane resins provides basecoat composition exhibiting low temperature flash characteristics. These low temperature flash characteristics are exhibited even where the basecoat is deposited at 50-90% relative humidity.

.Iadd.This application is a continuation of Reissue application Ser. No.07/379,244 filed Jul. 12, 1989 which is derived from U.S. Pat. No.4,791,168, issued Dec. 13, 1989.

BACKGROUND OF THE INVENTION

Multi-layer systems have been utilized to coat automobiles for a numberof years, but the early development of these systems necessarilyemployed organic solvents. As environmental regulations became morestringent, and the cost or organic solvents rose, organic-borne basecoatsystems became less desirable. The recent research emphasis in the areaof multi-layer systems, especially basecoat systems has focused on thedevelopment of water-borne systems for multi-layer coatings.

The shift from organic solvents to water for dispersing and applyingresins in multi-layer systems solved many of the environmental and costproblems associated with the use of organic solvents. Water-bornesystems, however, have resulted in other problems.

The application of a multi-layer coating to an automobile body, forexample, would be greatly facilitated by a system that provides forquick-drying of solvent during and after the application of a coating.These quick-drying characteristics enhance a broad application windowand allow minimal control of relative humidity and temperature in thespray zone, resulting in lower energy costs. By facilitating drying, thetime between coatings would be diminished, resulting in greatermanufacturing efficiencies and lower energy costs. In addition, therewould be no need for a cooldown zone after drying which would furtherthe manufacturing efficiencies. Low boiling organic solvents wereoriginally used in multi-layer coatings to take advantage of theirquick-drying features. With the introduction of aqueous basedmulti-layer systems, the drying of water from a given resin coatingafter application because a problem. It was desired to produce abasecoat composition that could be dried in a period of time shortenough to maintain manufacturing efficiency.

The present invention is directed to polyurethane coatings to be used informulating basecoat compositions of multi-layer coating systems. Theresins of this invention are shown to possess the qualities of beingquick-drying during and after application. Furthermore, the resins ofthis invention also exhibit superior coating characteristics, forexample, good metallic effects such as very favorable arrangement,fixation, and flip effect of the metallic pigments in the paint film.When non-metallic pigments are used, the resins of the present inventionexhibit excellent decorative effect.

This invention, therefore, relates to the field of polyurethane coatingsfor use in automobile basecoat/clearcoat systems. In particular, thisinvention relates to the discovery that incorporating a long-chaincarboxylic acid of at least 50% by weight of the carboxylic acidcomponent used to make polyester resins which are further incorporatedinto polyurethane resins provides basecoat compositions exhibiting lowtemperature flash characteristics. These low temperature flashcharacteristics are exhibited even where the basecoats are deposited at50-90% relative humidity.

The polyurethane resin, produced by the reaction of the above-describedpolyester resin and a polyisocyanate mixture, although useful as acoating composition for a number of substrates of especially useful as abasecoat for automobiles. Coatings containing polyurethanes synthesizedfrom polyesters with a long chain fatty acid comprising at least about50% of the acid component in the polyester resin have shown to beparticularly useful for water-borne basecoat compositions used inmulti-layer systems.

It is an object of this invention to provide polyurethane resins thatcan be incorporated into basecoat formulations to provide low flash andquick-drying characteristics.

It is an additional object of this invention to provide polyester resinswhich can provide favorable low flash and quick-drying characteristicsto polyurethane resins.

It is a further object of this invention to provide water-borne basecoatcompositions having favorable coating and cosmetic characteristics andadditionally provide for manufacturing efficiencies which result fromthe low-flash, quick-drying characteristics.

It is also an object of this invention to provide a method of producingthe resins and basecoat compositions described herein.

It is a further object of this invention to provide a method for coatinga metallic or plastic substrate utilizing the resins and basecoatformulations of the present invention.

These and other objects of the present invention are furthered byincorporating polyurethane resins into basecoat formulations.

SUMMARY OF THE INVENTION

The polyurethane resins are comprised of, in part, polyester resins froma carboxylic acid component and a alcohol having at least 2 hydroxylmoeities. Specifically, this invention relates to an anionicpolyurethane coating compositions comprised of:

1. A polyester component produced by condensing a carboxylic acidcomponent with alcohols having at least 2 hydroxy moeities wherein thecarboxylic acid component is comprised of at least about 50% by weightof a long chain hydrophobic carboxylic acid containing compound havingbetween 18 to 60 carbon atoms; and

2. A mixture of a compound having at least 2 isocyanate groups, amulti-functional compound having at least one active hydrogenfunctionality and at least one carboxylic acid functionality andoptionally, a compound having at least two active hydrogen groups, forexample, diols, dithiols, diamines, or compounds having mixtures ofthese active hydrogen groups, the polyester component described abovebeing reacted with this mixture to produce a polyurethane resincontaining free carboxylic acid groups. The free carboxylic acid groupsmay be neutralized to produce a water-dispersible polyurethane resin.

The polyurethane resin described above can be formulated as awater-dispersed basecoat resin along with a grind resin, a cross-linkingagent, thixotropic or rheology control agents, thickeners, pigments,aluminum and/or mica particles, basifying agents, water, fillers,surfactants, stabilizers, plasticizers, wetting agents, dispersingagents, adhesion promoters, defoamers, catalysts, and additionalpolymers, for example a branch-chain polyester among other ingredients.

After formulation, the basecoat composition can be sprayed orelectrostatically deposited onto the automobile body, preferably, in oneor two coats. Generally, two even coats of basecoat are applied with aone minute flash between coats. After deposition of the basecoat, beforeapplication of a high solids content clear coat, it is generallypreferred to flash about 90% of the water from the basecoat for optimumappearance and to eliminate water boil of the clearcoat.

A preferred embodiment of the water-dispersible anionic resin relates toa polyurethane product wherein the polyurethane is formed with a mixtureof an excess of diisocyanate, a multi-functional compound having atleast one active hydrogen functionality and at least one carboxylicacid, functionality and a hydroxy terminated polyester resin. Thismixture produces a urethane-containing resin intermediate having one ortwo free isocyanate groups per polymer chain. In especially preferredembodiments, the free isocyanate groups are than capped with an excessof an alcohol having a hydroxy functionality of at least one andpreferably, two or more.

The polyester component is preferably formed from an alcohol componenthaving at least about 2 hydroxy groups per molecule (polyol) and acarboxylic acid component. The carboxylic acid component is comprised ofat least about 50% by weight of a long chain carboxylic acid containingcompound having between 18 and 60 carbon atoms in the chain. Thislong-chain carboxylic acid component is an alkyl, alkylene, aralkyl,aralkylene, or compound of similar hydrophobicity having 18 and 60carbons in the chain. The polyester chain may be branched, but it ispreferred that chain-branching be kept to a minimum. It is recognizedthat low flash and quick-drying characteristics of the basecoatcompositions of this invention are the result of having a highpercentage of highly hydrophobic groups in the polyester resins. C18 toC60 carboxylic acid present a range of compounds having suitablehydrophobicity. Most preferably, this long chain carboxylic acid is adicarboxylic acid and most preferably is a C₃₆ dicarboxylic acid knownas a dimer acid. The remaining carboxylic acid component may becomprised of a short-chain monocarboxylic or dicarboxylic acidcomponent, preferably a dicarboxylic acid. When monocarboxylic acidcompounds are used, these function as polyester chain terminators. Thus,where high molecular weight polyesters are desired, the amount ofmonocarboxylic acid is kept to a minimum. The short-chain dicarboxylicacid may be preferably short-chain alkyl or alkalyne dicarboxylic acid,for example, azeleic acid, adipic acid, or an equivalent aliphaticdicarboxylic acid or an aromatic dicarboxylic acid. Most preferably, thearomatic dicarboxylic acid is isophthalic acid. It must be stressed thatwhile a number of short-chain carboxylic acid compounds may be used, theultimate goal is to maintain the hydrophobic, quick-flashcharacteristics of the polyester resin.

The polyester resins described hereinabove are useful on virtually anyelastomeric substrate and are particularly useful when formulated intopolyurethane coatings and used in basecoat formulations for depositiononto metal or plastic substrates, especially automobile bodies. Thepolyurethane resins synthesized from the above-described polyestersexhibit quick-drying, low flash characteristics. These polyurethaneresins are, of course, useful in embodiments where quick-drying,low-flash characteristics are required. These resins have shownparticular utility as a basecoat in a multi-layer basecoat/clear coatautomobile coating system.

The composition of the carboxylic acid component and polyol componentemployed to synthesize the polyester resins is such as to provide anexcess of the polyol over and above the total number of equivalents ofacid present in the mixture. In other words, the reactants should beselected, and the stoichiometric proportions of the respective acid andpolyol components be adjusted to give hydroxy-terminated, polyestermolecules each theoretically having a hydroxyl functionality of 2 ormore.

As stated above, the acid mixture employed in forming the polyesterintermediate most preferably contains a C₃₆ dicarboxylic acid productknown as dimer acid. Processes for forming this acid are well known andform the subject of numerous U.S. patents including U.S. Pat. Nos.2,482,761, 2,793,220, 2,793,221 and 2,995,121 or alternatively dimerfatty acid can be purchased from a chemical supply house (Empol 1010,available from Emery Chemical Co.).

C₃₆ dimer fatty acid fraction consists essentially of dimer (C₃₆dicarboxylic acids) together with amounts up to about 20-22% of C₅₄trimer. However, those of skill in the art refer to this dimer-trimermixture as "dimer", and this practice is followed herein. The preferredgrade contains 97% dimer and 3% trimer. These polymerization reactionproducts can be used in the form in which they are recovered from thepolymerization unit, or they can be given a partial or completehydrogenation treatment to reduce unsaturation before being reacted withthe polyol compound to form the polyester. Polyesters so formed can thenbe used to form a polyurethane resin which can be used in basecoatformulations exhibiting low flash, quick-drying characteristics.

The polyurethanes of the present invention are advantageously storagestable and are, of course, water dispersible. The water dispersibilityof the resins is controlled by the amount of free carboxylic acidcontained in the final resin particles, and the number of salts groupsformed from those free acid groups.

Coating compositions produced using the polyurethane resins describedherein have exhibited low flash and quick drying characteristicssurprising for a water-dispersible resin.

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to a water soluble anionic polyurethaneresin produced by reacting a polyester component comprised of at least50% by weight of the carboxylic acid component of a long chaincarboxylic acid containing compound with a mixture of apolyisocyanate-containing compound, a multifunctional compound having atleast one active hydrogen functionality and at least one carboxylic acidfunctionality, and optionally, an additional component comprising acompound having at least two active hydrogen containing moieties. Theresulting polyurethane intermediate has terminal isocyanate groups oractive hydrogen-containing moieties, depending upon the stoichiometry ofthe polyester mixture described above.

An especially preferred embodiment of the polyurethane resins of thepresent invention relates to the formation of a urethane product inwhich the intermediate polyurethane resin described above has freeisocyanate groups at the terminal positions of the polyurethane resin.The isocyanate groups are then capped with an excess of a polyfunctionalalcohol having at least 2 alcohol groups, and preferably at least 3alcohol groups.

The particular characteristics of the polyurethane resins are determinedby the components of the polyester resin. It has unexpectedly beendiscovered that polyester resins produced from a carboxylic acidcomponent comprised of at least about 50% by weight of a long fatty acidor dicarboxylic acid having between about 18 and 60 carbon atoms can beformulated into water-dispersible polyurethane coating resins exhibitingparticularly favorable low flash and quick drying properties for waterborne basecoat resins.

The acid component of the polyester is, of course, critical to theinvention and is comprised of a mixture of at least about 50% by weightof a long chain carboxylic acid component having between 18 and 60carbon atoms. Preferably, the long chain carboxylic acid is adicarboxylic acid and most preferably, the dicarboxylic acid is a C₃₆dimeric dicarboxylic acid or dimer acid. Where the long chain carboxylicacid comprises less than 100% of the carboxylic acid component, thecarboxylic acid component is also comprised of one or more short-chainedcarboxylic acids.

Preferably, the long chain fatty acid comprises between about 50 and 80%by weight of the acid component of the polyester polyol. In theprincipal resin (major vehicle) the long chain fatty acid componentcomprises about 75-80% of the a long chain fatty acid component and inthe grind resin, the polyester resin comprises about 50% by weight ofthe polyester resin. Generally, the higher the percentage of long chaincarboxylic acid, the better the quick-drying or flash offcharacteristics of the final polyurethane resin. However, theadvantageous flash-off characteristics must be balanced with the effectthat the change in the carboxylic acid component has on the metalliceffects, durability and other characteristics of the resin, including,in the case of grind resin, the ability to accomodate pigment.

The shorter chain carboxylic acid component is comprised of a mono-, di-or higher functionality carboxylic acid or a mixture of these carboxylicacids having carbon chains of 12 or fewer carbon units. Monocarboxylicacids function to terminate a polyester and are chosen for that purpose.It is preferable that the short chain carboxylic acid component be adicarboxylic acid. Such preferred dicarboxylic acid compounds include,for example, adipic, azeleic, and other aliphatic dicarboxylic acids.Aromatic dicarboxylic acids may also be preferred. As especiallypreferred aromatic dicarboxylic acid is isophthalic acid. Alkylene andaralkylene carboxylic acids can also be used. Where branch chains in thepolyester are desired, a carboxylic acid containing three or morecarboxylic acid groups, for example citric acid, is used. A preferredacid of this type is trimellitic anhydride.

The polyester resins are synthesized from the above-described carboxylicacid component and an excess of a polyol component. An excess of polyolis used so that the polyester resin preferably contains terminalhydroxyl groups. The polyol compounds preferably have an averagehydroxy-functionality of at least 2.

The polyester resin in most cases is comprised of one or more polyols,preferably a diol. Up to about 25 percent by weight of the polyolcomponent may be a polyol having three or more hydroxyl groups permolecule. Where polyols having three or more hydroxy groups are chosen,the result is a branched polyester.

While it is not always desirable to have a triol or highermulti-functional alcohol present because of the tendency to form abranched chain polyester, some branching may be desirable. The polyesterresin should not be highly branched, however. There may also be presenta small amount of monoalcohol, in the polyol component, particularly iflarger proportions of higher functional alcohols are used. Thesemonoalcohols serve as chain terminators. In certain instances, forexample, where certain high molecular weight polyols are used, thepolyols can be largely or even entirely made up of compounds offunctionality greater than two.

The diols which are usually employed in making the polyester resinsinclude alkylene glycols, such as ethylene glycol, propylene glycol,butylene glycol, and neopentyl glycol, 1,6 hexanediol and other glycolssuch as hydrogenated bisphenol A, cyclohexane dimethanol, caprolactonediol (i.e., the reaction product of caprolactyone and ethylene glycol),hydroxyalkylated bisphenols, and the like. However, other diols ofvarious types and, as indicated, polyols of higher functionality mayalso be utilized. Such higher functional alcohols can include, forexample, trimethylolpropane, trimethylolethane, pentaerythritol, and thelike, as well as higher molecular weight polyols.

The low molecular weight diols which are preferred in the instantinvention are known in the art. They have hydroxy values of 200 orabove, usually within the range of 2000 to 200. Such materials includealiphatic diols, particularly alkylene polyols containing from 2 to 18carbon atoms. Examples include ethylene glycol, 1,4-butanediol,cycloaliphatic diols such as 1,2 cyclohexanediol and cyclohexanedimethanol. An especially preferred diol is 1,6 hexanediol.

The resulting polyester resin is preferably produced with dimer fattyacid as the long chain carboxylic acid, isophthalic acid as the minorshort-chain carboxylic acid component component and an excess of 1,6hexane diol so that the resulting polyester polyol ranges in sizebetween about 200 and 2000 grams per equivalent of hydroxyl. Preferably,the polyester resin has a range between 700 and 800 grams per equivalentof hydroxyl and most preferably, has about 750 grams per equivalent ofhydroxyl.

To produce the polyurethane resins which are useful in basecoatcompositions of the present invention, the above-described polyesterpolyol is reacted with a mixture of a polyisocyanate, a multi-functionalcompound having at least one active hydrogen group and at least onecarboxylic acid group, and optionally, a component comprising a chemicalcompound having at least two active hydrogen groups, but no carboxylicacid groups.

The polyester, polyisocyanate and multi-functional compound may also bereacted in the same pot, or may be reacted sequentially, depending uponthe desired results. Sequential reaction produces resin which are moreordered in structure. Both the polyester and multi-functional compoundmay serve as chain extenders to build up the polyurethane backbonethrough reaction of hydroxyl groups with isocyanate groups. However, tofunction as a chain extender, the multi-functional compound must have atleast two active hydrogen groups. Where the multi-functional compoundhas only one active hydrogen group, the result is chain termination.Additional chain extenders having at least two active hydrogen groupsbut no carboxylic acid groups may be added to increase the chain lengthor to change the chemical characteristics of the polyurethane resin. Ingeneral, an excess of polyisocyanate is used so that an intermediatepolyurethane resin can be produced having free isocyanate groups at theterminal ends. The free isocyanate groups may then be preferably cappedwith trimethylol propane or diethanolamine.

The organic polyisocyanate which is reacted with the polyhydric materialas described is essentially any polyisocyanate and is preferably adiisocyanate, e.g., hydrocarbon diisocyanates or substituted hydrocarbondiisocyanates. Many such organic diisocyanates are known in the art,including p-phenylene diisocyanate, biphenyl 4,4'diisocyanate, toluenediisocyanate, 3,3'-dimethyl-4,4 biphenylene diisocyanate,1,4-tetramethylene diisocyanate, 1,6-hexamethylene diisocyanate,2,2,4-trimethylhexane-1,6-diisocyanate, methylene bis (phenylisocyanate), 1,5 naphthalene diisocyanate, bis(isocyanatoethylfumarate), isophorone diisocyanate (IPDI) and methylene-bis- (4cyclohexylisocyanate). There can also be employed isocyanateterminatedadducts of polyols, such as ethylene glycol, or 1,4-butylene glycol,trimethylolpropane etc. These are formed by reacting more than one mol.of a diisocyanate, such as those mentioned, with one mol, of polyol toform a longer chain diisocyanate. Alternatively, the polyol can be addedalong with the diisocyanate.

While diisocyanates are preferred, other multifunctional isocyanates maybe utilized. Examples are 1,2,4-benzene triisocyanate and polymethylenepolyphenyl isocyanate.

It is preferred to employ an aliphatic diisocyanate, since it has beenfound that these provide better color stability in the finished coating.Examples include 1,6-hexamethylene diisocyanate, 1,4-butylenediisocyanate, methylene bis(4-cyclohexyl isocyanate) and isophoronediisocyanate. Mixtures of diisocyanates can also be employed.

The proportions of the diisocyanate, polyester, and multi-functionalcompound are chosen so as to provide an isocyanate terminatedintermediate polyurethane resin. This can be accomplished by utilizing astoichiometric excess of polyisocyanate, i.e., more than one isocyanategroup per nucleophilic moiety (reactive with isocyanate) in the othercomponents.

For purposes of promoting water-solubility it is important to build acidgroups into the polyurethane. For example, the presence of acid groupsis capable of rendering the composition water-dilutable.

The acids that are employed to provide free acid groups in thepolyurethane resins of this invention are readily available. Theycontain at least one active hydrogen group and at least one carboxylicacid functionality. The active hydrogen group may be a thiol, a hydroxylor an amine, with primary amines being considered to have one activehydrogen group. Examples of such compounds include hydroxyl carboxylicacids, amino acids, thiol acids, aminothiol acids, alkanolamino acids,and hydroxythiol acids.

Compounds containing at least 2 hydroxyl groups and at least onecarboxylic acid are preferred. They can be prepared from an aldehydethat contains at least two hydrogens in the alpha position. Suchaldehydes are reacted in the presence of a base catalyst with twoequivalents of formaldehyde to form an 2.2-hydroxymethyl aldehyde. Thealdehyde is then gently oxidized to the acid by known procedures. Theacids that are employed in the invention can be represented insimplification by Formula I: ##STR1## wherein R representshydroxymethyl, hydrogen, or alkyl of up to 20 carbon atoms andpreferably up to 8 carbon atoms.

Specific illustrative examples of such acids that are employed in theinvention includes 2,2-di(hydroxymethyl) acetic acid,2,2,2-tri(hydroxymethyl) acetic acid, 2,2-di(hydroxymethyl) propionicacid, 2,2-di(hydroxymethyl)butyric acid, 2,2-di(hydroxymethyl)pentanoicacid, and the like. The preferred acid is 2,2-di(hydroxymethyl)propionic acid.

Longer-chain polyurethane resins can be obtained by chain extending thepolyurethane chain with a compound or mixture of compounds containing atleast two active hydrogen groups but having no carboxylic acid group,for example diols, dithiols, diamines, or compounds having a mixture ofhydroxyl, thiol, and amine groups, for example, alkanolamines,aminoalkyl mercaptans, and hydroxyalkyl mercaptans, among others. Forpurposes of this aspect of the invention both primary and secondaryamine groups are considered as having one active hydrogen.Alkanolamines, for example, ethanolamine or diethanolamine, arepreferably used as chain extenders, and most preferably a diol is used.Examples of preferred diols which are used as polyurethane chainextenders include 1,6 hexane diol, cyclohexanedimethylol, and1,4-butanediol. A particularly preferred diol is neopentylglycol. Ofcourse, the same diols used to synthesize the polyester component of thepolyurethane resins can be utilized here as well. While polyhydroxycompounds containing at least three hydroxyl groups may be used as chainextenders, the use of these compounds produces branched polyurethaneresins. For purposes of the present invention, it is preferred tominimize the amount of branching in the polyurethane resin. Therefore,if polyhydroxy compounds are used, they are preferably limited to a veryminor component of the polyurethane producing mixture. These higherfunctional polyhydroxy compounds include, for example,trimethylolpropane, trimethylolethane, pentaerythritol, among othercompounds.

The polyurethane resin may be chain extended in any manner using thesecompounds having at least two active hydrogen groups. Thus, thesecompounds may be added to the mixture of polyisocyanate, polyester andmulti-functional compound, or alternatively, may react at anintermediate stage, to link two free isocyanate groups that are presentat the terminal ends of an intermediate polyurethane resin.

It is generally preferred that an intermediate polyurethane resinproduced by reacting the polyester resin and the mixture ofpolyisocyanate, multifunctional compound containing at least 2 hydroxylgroups and one carboxylic acid group, and chain extender be terminatedwith free isocyanate groups. To accomplish this, an excess of thepolyisocyanate component is used. Of course, the molar ratio of theother components will be adjusted according to the desiredcharacteristics of the intermediate and final polyurethane resins. Thepolyester component comprises no more than about 80% by weight of thereaction mixture and it is preferred that the polyester componentcomprises from about 20% to about 70% by weight of reactants in themixture.

In one especially desirable embodiment of the invention, amulti-functional alcohol is used to terminate the reaction (cap the freeisocyanate groups) at the desired stage (determined by the viscosity andisocyanate groups present), thereby also contributing residual hydroxylgroups. Particularly desirable for such purposes are aminoalcohols, suchas ethanolamine, diethanolamine and the like, since the amino groupspreferentially react with the isocyanate groups present.Multi-functional alcohols, such as ethylene glycol, trimethylolpropaneand hydroxyl-terminated polyesters, can also be employed in this manner.

While the ratios of the components of the polyester, themulti-functional isocyanate and the terminating agent can be varied, itwill be noted by those skilled in the art that the amounts should bechosen so as to avoid gellation and to produce an ungelled, urethanereaction product containing hydroxyl groups. The hydroxyl value of theurethane reaction product should be at least 5 and preferably about 20to about 200.

The amount of polyisocyanate used in the mixture is preferably betweenabout 20% and 30% by weight of the reactants in the mixture, but willvary depending upon the polyester used, the acid number of the finalpolyurethane resin, and the desired molecular weight of the finalpolyurethane resin. The amount of polyisocyanate will also varydepending upon whether it is desired to have the intermediatepolyurethane terminated with free isocyanate groups or with hydroxylgroups. Thus, where it is preferred to terminate the intermediatepolyurethane resin with free isocyanates for capping withtrimethylolpropane or diethanolamine, an excess of polyisocyanate may beused. Where the intermediate polyurethane resin is to be terminated byhydroxyl groups, a stoichiometric deficiency of polyisocyanate may beused.

The amount of multi-functional component having at least one activehydrogen group and at least one carboxylic acid group also may varydepending upon the desired acid number of the final polyurethane resin.The final polyurethane resin has an acid number of at least about 10,and the amount of this multi-functional component comprises betweenabout 1% and about 25% by weight of the reactants of polyurethaneproducing reaction mixture (polyisocyanate, polyester, multifunctionalcompound, and optionally other chain extenders, for example compoundshaving two active hydrogens but no carboxylic groups). It is preferablethat the acid number be higher, because as the acid number increases,the water-dispersibility of the polyurethane resin potentiallyincreases. The practical upper limit of acid number is that whichnegatively effects the low flash or quick-drying characteristics andphysical properties of the final resin. Of course, the upper limit ofthe acid number will vary depending upon the chemical composition of thefinal polyurethane resin, but an acid number with an upper limit ofabout 100 is, in general, the practical limit of polyurethane resins ofthe present invention.

The amount of chain extender, when used producing the polyurethaneresin, varies between about 2% and 25% by weight of the reactants. Theamount used will depend upon the amount of chain extension desired andthe desired size of a polyurethane molecule.

After the polyurethane resin is synthesized, the free carboxylic acidgroups are neutralized with base to form salt groups. Preferably, thebase is an amino containing compound. Tertiary amines are generallypreferred over primary and secondary amines because of the tendency ofthe primary and secondary amines to react with aminoplast cross-linkingagents. Preferred tertiary amines include tri-alkylamines, for example,trimethyl and triethylamine. Also preferred is triethanolamine.Particularly preferred is dimethylethanolamine.

The polyurethane resins of the present invention are formulated, alongwith other components, into water dispersible basecoat compositionswhich are sprayed or electrostatically deposited onto metal or plasticsubstrates, for example, automobile bodies. In general, a polyurethaneresin formulated as described herein, is mixed with an aminoplast resin,pigments a grind resin, water, a portion of an organic solvent, aluminumand/or mica particles and a rheology control agent. Other agents may beincluded, for example, various fillers, surfactants, plasticizers,stabilizers, wetting agents, dispersing agents, defoamers, adhesionpromoters and catalysts in minor amounts. In one preferred embodiment abranched-chain polyester component is also added to the basecoatcomposition.

As indicated, an aqueous dispersion of the polyurethane resin isutilized as the principal or major vehicle resin. In general, theprincipal or major vehicle resin comprises between about 20 and 80% byweight of the total solids present in the basecoat composition. Thepreferred polyurethane resin is a resin produced from a polyestersynthesized from dimer fatty acid, isophthalic acid, and 1,6 hexanediol.The resulting polyester is then reacted with a diisocyanate ofisophorone, dimethylol propionic acid and a diol, for example, neopentylglycol. The resulting polyurethane intermediate having free isocyanategroups is then reacted with trimethylolpropane to cap these groups.

The polyurethane reaction product as described above is mixed with anaminoplast resin. Aminoplast resins are aldehyde condensation productsof melamine, urea, and similar compounds. Products obtained from thereaction of formaldehyde with melamine, urea or benzoguanamine are mostcommon and are preferred herein. However, condensation products of otheramines and amides can also be employed, for example, aldehydecondensates of triazines, diazines, triazoles, guanidines, guanaminesand alkyl and aryl substituted derivatives of such compounds, includingalkyl and aryl substituted ureas and alkyl and aryl substitutedmelamines. Some examples of such compounds are N,N'-dimethylurea,benzourea, dicyandiamide, formoguanamine acetoguanamine, ammeline,2-chloro-4,6-diamino-1,3,5-triazine,6-methyl-2,4-diamino,1,3,5-triazine, 3-5-diamino-triazole,triaminopyrimidine, 2-mercapto-4,6-diaminopyrmidine, 2,4,6-triethyltriamino-1,3,5-triazine, and the like.

While the aldehyde employed is most often formaldehyde, other similarcondensation products can be made from other aldehydes, for example,acetaldehyde, crotonaldehyde acrolein, benzaldehyde, furfural, andothers.

The amine-aldehyde condensation products contain methylol or similaralkylol groups, and in most instances at least a portion of thesealkylol groups are etherified by a reaction with an alcohol to provideorganic solvent-soluble resins. Any monohydric alcohol can be employedfor this purpose, including such alcohols as methanol, ethanol,propanol, butanol, pentanol, hexanol, heptanol and others, as well asbenzyl alcohol and other aromatic alcohols, cyclic alcohols, forexample, cyclohexanol, monoethers or glycols such as Cellosolves andCarbitols ™ (Union Carbide), and halogen-substituted or othersubstituted alcohols, such as 3-chloropropanol. The preferredamine-aldehyde resins are etherified with methanol or butanol.

A grind resin is also used in the basecoat compositions of the presentinvention. While the pigment resin may be comprised of a number of watersoluble polyurethane resins, it is preferred that the grind resin besimilar in chemical character to the principal or major vehicle resin,i.e., contain a polyester resin component comprised of a carboxylic acidcomponent comprised of at least about 50% by weight of a C18 to C60carboxylic acid, preferably a dicarboxylic acid. The grind resin mayrange between about 2 and about 75% by weight of the total solids in thecoating composition and will vary depending on the desired color andpreferably comprises about 5-40% by weight of the basecoat composition.

A preferred anionic polyurethane resin for use as a grind resin inembodiments of this invention is produced from a polyester polyolsynthesized from dimer fatty acid, adipic acid, and 1,6-hexane diol. Theresulting polyester diol is reacted with isophorone diisocyanate,dimethylol propionic acid and neopentyl glycol to produce a polyurethaneintermediate which is capped with diethanolamine.

Pigments may be incorporated into the basecoat to provide the desiredcosmetic characteristics. This is done by mixing pigments with theabove-described pigment resin and optionally, with other additives toform a pigment paste. Any standard pigment known in the art may be usedwith resins of the present invention so long as these pigments can beformulated without affecting the desired low flash and quick-dryingcharacteristics. Specific examples of the dye stuffs or pigments may beinorganic or organic, for example, graphite, carbon black, zincchromate, strontium chromate, barium chromate, lead chromate, leadcyanide, titanium dioxide, zinc oxide, cadmium sulfide, iron oxide,aluminum flakes mica flakes, zinc sulfide, phthalo cyanine complexes,naphthol red, quinacridones and halogenated thioindigo pigments, amongothers.

The preferred metallic pigments are metal powders preferably mixed withaluminum metal flakes. Preferred aluminum flake pigments are availablefrom Silberline Corp, Lansford, Pennsylvania or from Eckart Werke,Guenterstahl, West Germany. The aluminum flake pigments provide thecoating with an enhanced "metallic veneer". In a preferred embodiment ofthe present invention standard grade aluminum stabilized with phosphateester is used. Other metallic flake pigments, for example, silver mayalso be used but these are usually prohibitive in cost and inferior inappearance. The metallic pigments may also be mixed with non-metallicpigments, but these are to be carefully chosen so as not to diminish thedesired metallic effect.

The resins used in the basecoat are dispersed in deionized water. It ispreferred that the deionized water have conductance readings of lessthan 13 microohms⁻¹ and most preferably less than about 5 microohms⁻¹ toprevent gassing caused by the reaction of aluminum with water. Deionizedwater is also chosen to avoid salts that naturally occur in tap water.Other solvents may also be employed with the deionized water. Anespecially preferred solvent is Butyl Cellosolve ™ which aids mixing,formulating and dispersing pigment in the basecoat composition. Othersolvents can also be used, for example, low-boiling mono and polyhydricalcohols, ethers, esters, ketones and other organics. The organicsolvent, which comprises at most about 80% of the basecoat composition,and preferably comprises about 10% to 20% by weight of the basecoatcomposition (including water) may be selected to promote thedispersibility of individual components in the final basecoatcomposition (plasticizer characteristics) and for its low volatititycharacteristics.

A rheology control agent is also preferably incorporated into thebasecoat composition. The rheology control agent controls the viscosityof the resulting composition and is incorporated in amounts that willprevent sagging or running after a basecoat is sprayed onto a verticalsurface such as an automobile body. The direct result of incorporating arheology control agent is to provide flow control, body andsprayability. Other favorable results of adding a rheology control agentare to enhance the flip effect of metallic flake pigments, to deposit athicker coating, and to achieve complete coverage of a substrate. Thesprayed coatings containing these agents also exhibit greaterorientation of the metallic flake pigments on the final coatedsubstrate. Rheology control agents which can be used in embodiments ofthe present invention include the fumed silica compounds and thebentonite clays. Preferred fumed silica compounds are the hydrophobicsilica compounds, for example Aerosil R972, available from DeGussaCorporation, (Frankfurt, West Germany). Another rheology control agentwhich may be used, and in certain basecoat compositions, may bepreferred is a synthetic sodium lithium magnesium silicate hectoriteclay. An example of one such clay is Laponite RD, available fromLaporte, Inc (Saddlebrook, N.J.). In certain preferred embodimentsrheology control agents are mixed. The rheology control agent when it isincluded, generally comprises about 0.1 to about 20 percent by weight ofthe basecoat composition and preferably comprises between about 1percent and about 5 percent by weight of the final basecoat composition.

In general, the particle size of the rheology control agent plays a rolein the overall thixotropic properties of these resins. Rheology controlagents in embodiments of this invention are suspended in the material.It may be proposed that the rheology control agents are suspended andfunction, at least in part, through coulombic or electrostaticinteractions.

In general, the particle sizes can be from less than 0.1 microns to overabout 200 microns. These sizes can be adapted to develop in part therheology properties sought. In appropriate circumstances, the particlesizes may be from about 0.01 to about 10 microns.

In addition to a principal resin or major vehicle resin and a grindresin, peferred basecoat compositions also are comprised of at leastabout 5% by weight of the resinous vehicle of a branched-chain polyesterresin. The branched-chain polyester is added for improved applicationproperties and improved physical properties (due to increased cross-linkdensity). In general, the branched-chain polyester is produced from thesame components as the polyester component except that in addition tothe long and short chain carboxylic acid components, a small percentageof trifunctional acid or acid anhydride is used. Thus, the carboxylicacid component of the branch-chain polyester is comprised of at least50% by weight of a long-chain fatty acid, preferably C36 dimer fattyacid and no more than about 50% by weight of a combination of adicarboxylic acid such as isophthalic acid and a small percentage of atrifunctional carboxylic acid such as trimellitic anhydride. Inpreferred embodiments, the branched chain polyester is synthesized fromdimer fatty acid, isophthalic acid, and 1,6-hexane diol. A smallpercentage, about 5 to about 20% of trimellitic anhydride is added tothe polyesterification reaction to branch the polyester. The branchedchain polyester is cooked to a final acid number of 10-50, andpreferably, 20-40. In general, the branched polyester comprises about20% of the resinous vehicle, but may be lower depending on the color.

Any additional agent used, for example, surfactants, fillers,stabilizers, wetting agents, dispersing agents, adhesion promoters, etc.may be incorporated into the basecoat composition. While the agents arewell-known in the prior art, the amount used must be carefullycontrolled to avoid adversely affecting the coating and quick-dryingcharacteristics.

In formulating the basecoat compositions of the present invention, theorder of addition of the individual components is often very important.As a rule, the cross-linking agent in a solvent is added to the rheologycontrol agent in solution and thoroughly mixed. Thereafter, the majorvehicle resin dispersion (neutralized with amine) is added to therheology control solution under agitation. If desired, a slurry ofaluminum metal flakes and/or mica particles (mica particles are usedalone in the case where an aluminum metallic veneer is not desired) inButyl Cellosolve ™ is mixed with a premixed slurry of a branched-chainpolyester resin and dimethylethanolamine. This mixture of aluminum isthen agitated with the slurry containing resinous vehicle, cross-linkingagent, and rheology control agent. Pigment pastes comprised ofpolyurethane resin, pigment, fillers, stabilizers, plasticizers andother additives are then mixed under agitation with the above-resultingmixture. Pigment paste particles are prepared in a sand mill, attritoror other common milling equipment prior to use.

The pigment pastes may be prepared by mixing the aminoplast resin withabout 1/4 of the total polyurethane resin to be added to the pigmentpaste. Pigment is added to this slurry under agitation for about 1/2hour. The rest of the polyurethane resin is then added and the resultingpaste is mixed for another half-hour. The pH and viscosity of the pasteis checked and any adjustments are made by adding deionized water and/ortertiary amine. The weight ratio of pigment to binder usually rangesbetween 0.15-5.0. The amount of pigment ranges between 6 and 60% of thetotal weight of pigment plus binder. Other well-known methods offormulating prepared pigment pastes may also be used.

The final basecoat composition is adjusted to a pH of 7.6-7.8 with atertiary amine, for example, N-ethylmorpholine. Viscosity may beadjusted using deionized water. Final basecoat compositions arecomprised of the following components in the indicated weight ratios.

                  TABLE I                                                         ______________________________________                                                         Amount (% by weight of                                                        Solids of Final Basecoat                                     Ingredient       composition)                                                 ______________________________________                                        Polyurethane resin                                                                             20-80%                                                       Melamine         5-50%                                                        Rheology Control Agent                                                                         0-20%                                                        Branched chain Polymer                                                                         0-35%                                                        Pigment          2-65%                                                        ______________________________________                                    

The basecoat compositions described hereinabove can be applied to ametal or plastic substrate in one or two coats using for example an airatomizer (Binks Model 60 spray gun, available from Binks ManufacturingCorporation, (Franklin Park, Ill.), or by using other conventionalspraying means. The basecoat compositions may also be appliedelectrostatically. The basecoat compositions are preferably sprayed at50-80 psi, and a relative humidity of between 50 and 90% (optimally at60-80% relative humidity) and a temperature of 70°-90° F.

After being deposited, the basecoat compositions are flash dried withina temperature range of about room temperature to about 145 degrees F.for between 30 second and about 10 minutes using warm air blowing at arelative humidity of 5-40%. The preferred flash temperature is about 120degrees F. which is carried out for preferably between about 1 and 5minutes. The flash conditions described herein result in about 90-95% ofthe solvents (water plus organics) being flashed from the basecoat inthis short period of time.

After the first basecoat is deposited, a second basecoat can bedeposited over the first without drying (flash off), or alternatively, aclearcoat may be deposited over the flashed basecoat. Any number ofclearcoat compositions known in the art may be used. Any knownunpigmented or other transparently pigmented coating agent is inprinciple, suitable for use as a clearcoat. A typical top coatcomposition contains 30-70% film forming resin and 30-70% volatileorganic solvent.

After the clear coat is coated onto the basecoat layer, the multi-layercoating is then baked to cross-link the polymeric vehicle and to drivethe small amount of residual water and organic solvent from themulti-layered polymeric composition. A preferred baking step involvesheating the coated substrate for a period of 10-60 minutes at atemperature of between 150 and 300 degrees F. The baking step cures thecoating to a hard, durable film.

The invention will be further described in connection with severalexamples which follow. These examples are shown by way of illustrationof the invention and are not meant to limit the scope of the invention.All parts and percentages in the examples are by weight unless otherwiseindicated.

POLYURETHANE EXAMPLE 1 Preparation of a Polyurethane Resin

A polyester polyol resin is prepared by charging a reaction vessel(flask with a fractionating column) with 551.9 g. (15.8% of thepolyester resin) of isophthalic acid, 1923 g. (54.9%) Empol 1010 (dimerfatty acid available from Emery Chemical Co.), and 1025.1 g. (29.3%) of1,6-hexanediol and 100 g. of toluene. Additional toluene may be added tofill the trap. The mixture was heated under nitrogen and the water ofconcondensation was removed. During this heating 235.7 g. of water wasdistilled off. Heating was continued at approximately 200 degrees C.until the acid number is less than or equal to 8. The remaining tolueneis then vacuum stripped at 220° C. to produce a polyester resin for usein the polyurethane resin.

At this point, 697.9 g. of the above-synthesized polyester resin 43.0 g.of dimethylol propionic acid, 16.1 g. of neopentylgylcol, 234.0 lbs. ofIsophorone diisocyanate and 300 g. of methyl isobutyl ketone are chargedto a the reactor and heated at reflux (about 128 degrees C.) until aconstant isocyanate value is obtained. 36.8 g. of trimethylol propane isthen added to the reactor and the batch is allowed to reflux for anadditional one hour. At this point, the nitrogen purge is turned off andthe batch is cooled to 95 degrees C. 28.6 g. of dimethylethanolamine and100 lbs of water is then added using a portion of the water as a rinse.The batch is then allowed to sit until it becomes homogeneous (about 5minutes) and then 2048.71 g. of water is added over a 20 minute periodunder vigorous agitation.

At the end of this addition the mixture is distilled on high heat withvigorous agitation to remove water and methyl isobutyl ketone. The wateris then returned to the batch and the approximately 300 grams of methylisobutyl ketone which was distilled off is discarded. 238 g. ofn-butanol is added and the batch is held at 80 degrees C. for 30minutes. The batch is then dropped and filtered through a 10 micronfilter to give a polyester-urethane vehicle for use in the basecoatcomposition of the invention. The resulting dispersion has a solidscontent of 30% and a Gardner viscosity of Z2.

Polyurethane Dispersion 2 Preparation of Polyester Resin

A reaction vessel is charged with 1995 g. of adipic acid, 1995 g. ofdimer acid, and 2450 g. of 1,6-hexanediol, and 136 g. toluene. Themixture is heated under nitrogen to 209 degrees C., removing water untilan acid number less than 8 is reached. Remaining toluene is vacuumstripped to produce a polyester resin having solids content greater than98%.

Polyurethane Dispersion Preparation

857.4 g. of the above polyester is mixed with 14.6 g. neopentyl glycol,53.1 g. dimethylolpropionic acid, 306.5 g. isophorone diisocyanate, 97.1g. methyl ethyl ketone, and 235.0 g. methyl amyl ketone are refluxeduntil a constant isocyanate value is obtained. At this point, 24.8 g. ofdiethanolamine is added and the mixture is held for 30 minutes. 24.8 g.of dimethylethanolamine and 116.8 g. deionized water and 118.2 g.isopropyl alcohol are added and allowed to mix for 15 minutes. 3123.2 g.deionized water is then added over a 20 minute period with vigorousagitation. The resulting dispersion has a solids content of 26% and anappropriate Gardner viscosity.

Polyurethane Dispersion 3 Preparation of Polyester

770 g. dimer acid, 230 g. 1,6-hexanediol, and 25 g. toluene are chargedand the resulting mixture heated to 200 degrees C. Heating is continued,removing water, until an acid number less than 10 is achieved. Theremaining toluene is then removed under vacuum.

Polyurethane

700 g. polyester above, 12.6 g. neopentyl glycol, 43 g.dimethylolpropionic acid, 244 g. isophorone diisocyanate, 77.8 g. methylethyl ketone, and 195.3 methyl amyl ketone are reacted using theprocedure for polyurethane dispersion 2. The resulting dispersion has asolids content of 26% and a Gardner viscosity of Z1.

Branched Polyester 1

2594 g. of dimer acid, 2564 g. of 1,6-hexanediol, and 744 g. ofisophthalic acid are charged and the mixture heated to 195 degrees C.under nitrogen with agitation until acid number of 10 or less isreached. The mixture is then cooled to 150 degrees C. and 1000 g. oftrimellitic anhydride is added slowly, and refluxed until an acid numberof 30-32 is reached. After cooling to 150 degrees C. or less, 729 g. ofbutyl Cellosolve ™ and 1459 g. of n-butanol are added. The resultingpolyester has a solids content of 70% and a Gardner viscosity of U-V.

Branched Polyester 2

1230 g. dimer acid and 769.5 g. 1,6 hexanediol, are charged and heatedto 195 degrees C. under nitrogen with agitation. Heating is continueduntil an acid number less than 10 is reached. The mixture is then cooledto 150 degrees C. and 420.1 g. trimellitic anhydride is added slowly andheated until the acid number falls below 30. 335 g. butyl glycol and 670g. n-butanol are then added with agitation. The resulting polyestersolution has a solids content of 70% and a Gardner viscosity of Z1.

Branched Polyester 3

868.7 g 1,6-hexanediol, 1346.2 g. dimer acid, and 386 g. isophthalicacid are heated at 195 degrees C. until an acid number less than 8 isachieved. 206.6 g. trimellitic anhydride is then added slowly underagitation and heat applied until an acid number less than 30 isachieved. A 2:1 mixture of n-butanol and butyl glycol are then added,until 70% solids is reached. The resulting branched polyester resin hada Gardner viscosity of U.

PREPARATION OF COATING AGENTS

The composition of the coating agents is shown in Table 2, where thenumbers denote parts by weight. The following notes refer to componentslisted there: Thickener 1: Paste of Aerosil R972 (Degussa) hydrophobicfumed silica sand milled with appropriate polyurethane grind resin andmelamine in water, organic solvent mixture at 11% strength.

Thickener 2: Paste of synthetic sodium lithium magnesium silicatehectorite clay, Laponite RD (Laporte), 2% strength is deionized water;the paste is prepared by stirring with Cowles blade in water for onehour.

Thickener 3: Paste of Laponite RD 3% strength in deionized water.Prepare as Thickener 2.

Titanium Dioxide Pigment Paste: 41% concentration of DuPont R-960titanium dioxide sandmilled with appropriate polyurethane grind resinand melamine.

Melamine Resin: Commercially available methanoletherfiedmelamine/formaldehyde resin, solids content 90% by weight in n-butanol.

Aluminum Pigment I: Silberline SS-5251 AR post treated with 4.5%Vircopet 40 (phosphate ester commercially available from Albright &Wilson, Richmond, Va.)

Aluminum Pigment II: Stapa Hydrolac WH-R607 from Eckart Werke

Aluminum Pigment III: Stapa Hydrolac WH-8487 from Eckwart Werke

    ______________________________________                                                     1   2     3     4   5   6   7   8   9                            ______________________________________                                        Thickener 2    40    37        37  38                                         Thickener 3                25                  13  13                         Melamine Resin 4     4     4   4   8   7   4   1   2                          Butyl Cellosolve                                                                             1     1     1   1   1   2           1                          Polyurethane 1 40              40                  18                         (30% NV)                                                                      Polyurethane 2       44            42      38  17                             (26% NV)                                                                      Polyurethane 3             44          38                                     (26% NV)                                                                      Aluminum I (54% NV)                                                                          6               6           6                                  Aluminum II (65% NV) 5                                                        Aluminum III (65% NV)      5       6                                          Butyl Cellosolve                                                                             1     1     1       4   2   1                                  Polyester 1 (70%)                                                                            6                           6   3                              Polyester 2 (70%)          6   6                                              Polyester 3 (70%)    6                                                        Dimethylethanolamine                                                                         2     2     2   2   1   6   6   1                              5% Strength in Water                                                          Thickener 1                            27  27  17  17                         Titanium Dioxide Paste                         48  49                         Deionized Water            12  4       12  12                                 ______________________________________                                    

EXAMPLES 1 TO 4

The melamine resin and Butyl Cellosolve are premixed and added to thethickener under agitation. The polyurethane dispersion is then added tothis mixture under agitation. An aluminum slurry is made by first mixingthe aluminum pigment and butyl cellosolve then adding the polyesterresin, and then finally preneutralizing this slurry with the 5% DMEAsolution. The aluminum slurry is then added to thepolyurethane/thickener/melamine mixture under agitation.

EXAMPLE 5

Half of the melamine resin and butyl Cellosolve ™ are premixed and addedto the thickener under agitation. The polyurethane dispersion is thenadded. An aluminum slurry is made separately by mixing the aluminumpigment, remaining butyl Cellosolve ™ and melamine resin. The aluminumslurry is then added under agitation to the rest of the paint. The pH isthen adjusted with 5% dimethylethanolamine in water.

EXAMPLE 6

An aluminum slurry is made with aluminum pigment, melamine resin, andButyl Cellosolve under agitation. The polyurethane dispersion is addedto the aluminum slurry. Thickener is then added under agitation. pH isadjusted with 5% DMEA and viscosity is adjusted with deionized water.

EXAMPLE 7

The polyurethane dispersion, melamine resin, and Butyl Cellosolve aremixed with agitation. An aluminum slurry is made as in Example 1 to 5and added to the first mixture under agitation. The thickener is addedunder agitation. Viscosity is adjusted with deionized water.

EXAMPLES 8 AND 9

Melamine resin and Butyl Cellosolve are premixed and added underagitation to Thickener 3. The polyurethane dispersion is then addedunder agitation. In Example 8, the polyester resin is preneutralizedwith 5% DMEA and then added under agitation. Thickener 1 (R972 paste) isadded and then the titanium dioxide paste is added both under agitation.

The invention has been described in detail with particular reference topreferred embodiments thereof, but it will be understood that variationsand modifications can be affected within the spirit and scope of theinvention and that the scope of the invention is to be determined by theclaims appended hereto.

.[.1. A basecoat composition suitable for deposition onto metal orplastic comprising: acid..].
 3. The basecoat composition according toclaim .[.2.]. .Iadd.57 .Iaddend.wherein said long-chain carboxylic acidcomprises about 50 to 80% of the carboxylic acid component used tosynthesize said polyurethane principal resin. .[.4. The basecoatcomposition according to claim 3 wherein said long chain carboxylic acidused to synthesize said polyurethane resin is C₃₆ dimer fatty acid..]..[.5. The basecoat composition according to claim 1 wherein saidpolyfunctional carboxylic acid (d) is trimellitic anhydride..].
 6. Thebasecoat composition according to claim .[.1.]. .Iadd.60.Iaddend.wherein said hectorite clay is a purified sodium lithiummagnesium silicate.
 7. The basecoat composition according to claim.[.1.]. .Iadd.61 .Iaddend.wherein said fumed silica compound is Aerosil972 ™. .[.8. The basecoat composition according to claim 1 wherein saidaminoplast is melamine..].
 9. A branched chain polyester resin for usein basecoat compositions comprising the reaction product of:(a) apolyester component comprised of the reaction product of(i) a carboxylicacid component comprised of at least about 50% by weight of a long-chaincarboxylic acid having between 18 and 60 carbons, no more than about 50%by weight of a short-chain dicarboxylic acid; and (ii) an alcoholcomponent having an average functionality of at least 2; and (b) betweenabout 2 and 25% by weight of a polyfunctional carboxylic acid or acidanhydride having at least 3 carboxylic acid groups.
 10. The polyesterresin according to claim 9 wherein said long-chain carboxylic acid isC36 dimer fatty acid.
 11. The polyester resin according to claim 9wherein said short-chain dicarboxylic acid is isophthalic acid.
 12. Thepolyester resin according to claim .[.11.]. .Iadd.65 .Iaddend.whereinsaid polyfunctional carboxylic acid is trimellitic anhydride.
 13. Thepolyester resin according to claim .[.12.]. .Iadd.66 .Iaddend.whereinsaid aliphatic diol is 1,6 hexanediol.
 14. A multi-layer paintcomposition comprising:(a) at least one waterborne basecoat compositioncomprising:(i) an anionic polyurethane composition comprised of thereaction product of:(1) a polyester resin component produced by thereaction of a carboxylic acid component comprised of at least 50% byweight of at least one long-chain carboxylic acid having between 18 and60 carbon atoms, and at most about 50% by weight of a short-chaindicarboxylic acid and an alcohol having at least 2 hydroxyl groups; and(2) a mixture of at least one multi-functional compound having at least1 active hydrogen group and at least two active hydrogen groups, and apolyisocyanate, said carboxylic acid groups being neutralized with anamine; (ii) a cross-linking agent; (iii) a branched chain polyesterresin comprised of the reaction product of:(1) (A) a polyester componentcomprised of the reaction product of a carboxylic acid componentcomprised of at least 50% by weight of a long-chain carboxylic acidhaving between 18 and 60 carbons, no more than about 50% by weight of ashort-chain dicarboxylic acid; and (B) an alcohol containing compoundhaving an average alcohol functionality of at least 2; and (2) betweenabout 2 and 25% by weight of a poly-functional carboxylic acid or acidanhydride having at least 3 carboxylic acid groups; (iv) a pigment; and(b) a clear topcoat composition for overcoating said basecoatcomposition. .[.15. The composition according to claim 14 wherein saidlong-chain carboxylic acid is C₃₆ dimer fatty acid..].
 16. Thecomposition according to claim .[.15.]. .Iadd.67, 68, or 69.Iaddend.wherein said cross-linking agent is melamine. .[.17. Thecomposition according to claim 16 wherein said short chain dicarboxylicacid is isophthalic acid..].
 18. The composition according to claim 14wherein said compound having at least two active .Iadd.hydrogen.Iaddend.groups .Iadd.of component (a) (i)(2) .Iaddend. is selected fromthe group consisting of diols, diamines, and dithiols.
 19. Thecomposition according to claim .[.14.]. .Iadd.74 .Iaddend.wherein saidaliphatic diol is 1,6 hexanediol.
 20. The composition according to claim14 wherein said polyfunctional carboxylic acid is trimellitic anhydride.21. The .[.method.]. .Iadd.composition .Iaddend.according to claim 20wherein said long-chain carboxylic acid .Iadd.of component (a)(i)(1).Iaddend.is C₃₆ dimer acid.
 22. The .[.method.]. .Iadd.composition.Iaddend.according to claim 21.Iadd., 75 or 76 .Iaddend.wherein saidshort-chain dicarboxylic acid is selected from the group consisting ofadipic acid and isophthalic acid.
 23. The .[.method.]. .Iadd.composition.Iaddend.according to claim 22 wherein said alcohol having at least 2hydroxyl groups is 1,6-hexanediol.
 24. The .[.method.]..Iadd.composition .Iaddend.according to claim 23 wherein saidcross-linking agent is melamine.
 25. The .[.method.]. .Iadd.composition.Iaddend.according to claim .[.24.]. .Iadd.79 .Iaddend.wherein saidrheology control agent is selected form the group consisting of fumedsilica compounds, bentonite clays, and hectorite clays.
 26. The.[.method.]. .Iadd.composition .Iaddend.according to claim 25 whereinsaid hectorite clay is a purified sodium lithium magnesium silicate. 27.A method of coating an automobile substrate with a multilayer coatingcomprising:(a) applying to the primed substrate .[.old.]. at least onelayer of a waterborne .[.coating.]. .Iadd.basecoat .Iaddend.compositioncomprised of:(i) a polyurethane resin obtained from the reaction productof:(1) a polyester resin component produced by the reaction of acarboxylic acid component comprised of at least 50% by weight of along-chain carboxylic acid having between 18 and 60 carbon atoms and atmost about 50% of a short chain dicarboxylic acid and an alcohol havingat least 2 hydroxyl groups; and (2) a mixture of a multi-functionalcompound having at least 1 active hydrogen functionality and at leastone carboxylic acid functionality, at least one compound having at leasttwo active hydrogen groups, and polyisocyanate, said carboxylic acidgroups being neutralized with an amine; (ii) a cross-linking agent;(iii) a rheology control agent; and (iv) a pre-formed branched chainpolyester resin comprised of the reaction product of:(1) (A) a polyestercomponent comprised of the reaction product of a carboxylic acidcomponent comprised of at least 50% by weight of a long chain carboxylicacid having between 18 and 60 carbons, no more than about 50% by weightof a short-chain dicarboxylic acid and between about 2 and 25% by weightof a poly-functional carboxylic acid having at least 3 carboxylic acidgroups; and (B) an alcohol component having an average functionality ofat least 2; and (2) between about 2 and 25% by weight of apolyfunctional carboxylic acid having at least 3 carboxylic acidgroups,(b) flash drying said basecoats; and (c) applying at least onelayer of a clear topcoat onto said basecoat; and (d) curing saidbasecoats and topcoat to a hard, durable film.
 28. The method accordingto claim 27 wherein said long-chain carboxylic acid is C₃₆ dimer fattyacid .Iadd.of component (a)(i)(1).Iaddend..
 29. The method according toclaim 28.Iadd., 81 or 82 .Iaddend.wherein said short-chain dicarboxylicacid .Iadd.of component (a)(i)(1) .Iaddend.is isophthalic acid.
 30. Themethod according to claim 29 wherein said alcohol having at least 2hydroxyl groups is 1,6 hexane diol.
 31. A multi-coated metal or plasticsubstrate comprising:a substrate coated with at least one waterbornebasecoat composition comprising: (a) about 20 to 80% weight percentbased on the final solids content of said basecoat composition of .[.afirst.]. .Iadd.an .Iaddend.anionic polyurethane resin comprised of thereaction product of:(i) a polyester component with an alcohol having atleast two hydroxyl groups .[.wherein said.]. .Iadd.and a.Iaddend.carboxylic acid component .[.is.]. comprised of at least about50% by weight of a long-chain carboxylic acid having between 18 and 60carbon atoms and at most about 50% of a short chain dicarboxylic acid:(ii) a multi-functional compound having at least 1 active hydrogenfunctionality and at least one carboxylic acid functionality; (iii) acompound having at least 2 active hydrogen groups; (iv) apolyisocyanate; and (v) an amine-containing compound for neutralizingthe free carboxylic acid groups; (b) about 5 to about 50 weight percentof an aminoplast cross-linking resin; (c) about 0.1 to about 25 weightpercent of a rheology control agent, selected from the group consistingof fumed silica compounds, bentonite clays, and hectorite clays; (d)about 0 to about 35 weight percent of a branched chain polyester resincomprised of the reaction product of;(i) a carboxylic acid componentcomprised of at least 50% by weight of a long chain carboxylic acidhaving between 18 and 60 carbons, no more than about 48% by weight of ashort-chain dicarboxylic acid and between 2 and 25% by weight of apolyfunctional carboxylic acid or acid anhydride, said polyfunctionalcarboxylic acid having at least 3 carboxylic acid groups; and (ii) analcohol component having an average functionality of about at least 2;and (e) about 2 to about 75 weight percent of a pigment, each of saidbasecoat compositions being flash-dried before being coated with a cleartopcoating, said basecoat composition and said topcoating being cured toa hard, durable film.
 32. The composition according to claim 31 whereinsaid long-chain carboxylic acid .Iadd.of component (a)(i)(1) .Iaddend.isC₃₆ dimer acid.
 33. The composition according to claim .[.1.]. .Iadd.31.Iaddend.wherein said polyurethane resin is neutralized with an amine.34. The composition according to claim 33 wherein said amine is atertiary amine.
 35. The composition according to claim 14 wherein saidamine is a tertiary amine.
 36. The .[.method.]. .Iadd.composition.Iaddend.according to claim 21 wherein said amine is a tertiary amine..[.37. The method according to claim 21 wherein said premixed slurry isfurther comprised of pigment particles..].
 38. The .[.method.]..Iadd.composition .Iaddend.according to claim .[.37.]. .Iadd.89.Iaddend.wherein said pigment particles are selected from the groupconsisting of aluminum metal flakes and pigment coated mica particles.[.in solvent.]..
 39. The method according to claim 27 wherein saidamine is a tertiary amine. .[.40. The method according to claim 27wherein said first layer composition further comprises a compositionselected from the group consisting of aluminum, mica, and mixturesthereof..].
 41. The method according to claim .[.27.]. .Iadd.90.Iaddend.wherein said first layer .[.composition.]. further comprises abranched polyester resin.
 42. The method according to claim .[.40.]..Iadd.91 .Iaddend.wherein said first layer further comprises a branchedpolyester resin.
 43. The method according to claim 31 wherein saidamine-containing compound is a tertiary amine-containing compound..[.44. The basecoat composition of claim 1, wherein the rheology controlagent is selected from the group consisting of fumed silica compounds,bentonite clays, and hectorite clays..].
 45. The multi-layer paintcomposition of claim 14 wherein said topcoat composition is applied tothe uncured basecoat compositions which have been flash dried at a timeand temperature such that the topcoat can be applied without anintervening cooldown period.
 46. The multi-layer paint composition ofclaim 45 wherein the basecoat compositions are flash dried at atemperature between room temperature and about 145 degrees F. forbetween about 30 seconds and about 10 minutes.
 47. The multi-coatedmetal or plastic substrate of claim 31 wherein the basecoat compositionsare flash dried at a time and temperature such that the topcoat can beapplied without an intervening cooldown period.
 48. The multi-coatedmetal or plastic substrate of claim 47 wherein the basecoat.[.composition.]. .Iadd.compositions .Iaddend.are flash dried at atemperature between room temperature and about 145 degrees F. forbetween about 30 seconds and about 10 minutes.
 49. The basecoatcomposition of claim .[.1 additionally.]. .Iadd.59 .Iaddend.comprisingfrom about 2 to about 25 weight percent of a rheology control agent. 50.The basecoat composition of claim 49 wherein the rheology control agentis selected from the group consisting of fumed silica compounds,bentonite clays and hectorite clays.
 1. A method of making a waterbornebasecoat composition for use in a multi-layer coating comprised of(A) ananionic polyurethane resin comprised of(1) a polyester resin componentproduced by the reaction of a carboxylic acid component comprised of atleast 50% by weight of a long-chain acid having between 18 and 60 carbonatoms and at most about 50% of a short-chain dicarboxylic acid and analcohol having at least 2 hydroxyl groups; and (2) a mixture of at leastone multi-functional compound having at least 1 active hydrogenfunctionality and at least one carboxylic acid functionality, at leatone compound having at least two active hydrogen groups, and apolyisocyanate, said carboxylic acid group being neutralized with anamine, (B) a crosslinking agent, and (C) a rheology control agent,comprising the sequential steps of:(a) adding the crosslinking agent insolution to the rheology control agent in solution and thoroughly mixing.Iadd.and.Iaddend.; (b) adding an aqueous dispersion of the anionicpolyurethane resin under agitation and thoroughly mixing.
 52. The methodof claim 51 comprising the additional sequential step of (c) addingunder agitation and with thourough mixing a premixed slurry comprisedof:(i) a slurry of mica particles and, optionally, aluminum metal flakesand (ii) a pre-formed branched chain polyester resin dispersions, saidpolyester resin comprised of the reaction product of:(1) (A) a polyestercomponent compound of the reaction product of a carboxylic acidcomponent comprised of at least 50% by weight of a long chain carboxylicacid having between 18 and 60 carbons, no more than about 50% by weightof a short-chain dicarboxylic acid and between about 2 and 25% by weightof a polyfunctional carboxylic acid having at least 3 carboxylic acidgroups; and (B) an alcohol component having an average functionality ofat least 2; and (2) between about 2 and 25% by weight of apolyfunctional carboxylic acid having at least 3 carboxylic acid groups.53. The method of claim 52 comprising the additional sequential steps of(d) adding under agitation and with thorough mixing a pigment-containinggrind resin, and (e) adjusting the pH and viscosity of the mixture soobtained.
 54. The method of claim 27 wherein the basecoat compositionsare flash dried at a time and temperature such that the topcoat can beapplied without an intervening cooldown period.
 55. The method of claim54 wherein the basecoat compositions are flash dried at a temperaturebetween room temperature and about 145 degrees F. for between about 30seconds and about 10 minutes. .Iadd.56. A basecoat composition fordeposition onto metal or plastic comprising:(a) about 20 to 80% weightpercent based on the final solids content of said basecoat compositionof an anionic polyurethane resin comprised of the reaction productof:(i) a polyester component comprised of the reaction product of acarboxylic acid component with an alcohol having at least two hydroxylgroups wherein said carboxylic acid component is comprised of at leastabout 50% by weight of at least one long-chain carboxylic acid havingbetween 18 and 60 carbon atoms and at most about 50% of at least oneshort-chain dicarboxylic acid; (ii) a multifunctional compound having atleast one active hydrogen and at least one carboxylic acidfunctionality; (iii) a compound having at least 2 active hydrogen groupsselected from the group consisting of hydroxyl, sulfhydryl, primaryamine and secondary amine, one of said primary amines accounting for oneactive hydrogen and (v) a polyisocyanate; (b) about 5 to about 50% byweight of an aminoplast cross-linking resin; (c) 5 to about 35 weightpercent of a branched chain polyester resin comprised of the reactionproduct of:(i) a polyester component comprised of the reaction productof:(1) a carboxylic acid component comprised of at least 50% by weightof at least one long chain carboxylic acid containing compound havingbetween 18 and 60 carbons and not more than 50% by weight of at leastone short-chain dicarboxylic acid, and (2) an alcohol component havingan average functionality of at least 2; and (ii) 2 to 25% by weight of apolyfunctional carboxylic acid or acid anhydride, said polyfunctionalcarboxylic acid or acid anhydride having at least 3 carboxylic acidgroups; and (d) about 2 to 75 weight percent of pigment-containing grindresin comprising:(i) about 6 to about 60% by weight of saidpigment-containing grind resin of a pigment; (ii) about 20 to about 75%by weight of said pigment-containing grind resin of a polyurethane resinproduced by the reaction product of:(1) a polyester resin componentproduced by the reaction of a carboxylic acid component comprised of atleast 50% by weight of a long-chain carboxylic acid having between 18and 60 carbon atoms, and at most about 50% of a short-chain dicarboxylicacid, and an alcohol having at least 2 hydroxyl groups; and (2) amixture of a multifunctional compound having at least 1 active hydrogenand at least one carboxylic acid functionality, and at least onecompound having at least two active hydrogen groups, and apolyisocyanate, said at least one carboxylic acid functionality beingneutralized with amine; and (iii) about 20% to about 60% by weight ofsaid pigment-containing grind resin of an aminoplast cross-linkingagent. .Iaddend. .Iadd.57. The basecoat according to claim 56, whereinthe long-chain carboxylic acid contained in the polyurethane resin ofcomponent (a) is comprised of C₃₆ dimer fatty acid. .Iaddend. .Iadd.58.The basecoat composition according to claim 56 wherein themultifunctional compound of component (d)(ii)(2) is trimelliticanhydride. .Iaddend. .Iadd.59. The basecoat composition according toclaim 56 further comprising a rheology control agent. .Iaddend..Iadd.60. The basecoat composition according to claim 59 wherein therheology control agent is hectorite clay. .Iaddend. .Iadd.61. Thebasecoat composition according to claim 59 wherein the rheology controlagent is a fumed silica compound. .Iaddend. .Iadd.62. The basecoatcomposition of claim 57 wherein the aminoplast cross-linking agent ofcomponent (b) is an aldehyde condensation product of melamine. .Iaddend..Iadd.63. The basecoat composition of claim 57 wherein the aminoplastcross-linking agent of component (d)(iii) is an aldehyde condensationproduct of melamine. .Iaddend. .Iadd.64. The basecoat composition ofclaim 57 wherein the aminoplast cross-linking resin of components (b)and (d)(iii) is an aldehyde condensation product melamine. .Iaddend..Iadd.65. The polyester resin of claim 9 wherein component (b) is apolyfunctional carboxylic acid. .Iaddend. .Iadd.66. The polyester resinof claim 9 wherein the alcohol component is an aliphatic diol. .Iaddend..Iadd.67. The composition of claim 14 wherein the long-chain carboxylicacid of component (a)(i)(1) is C₃₆ dimeter acid. .Iaddend. .Iadd.68. Thecomposition of claim 14 wherein the long-chain carboxylic acid ofcomponent (a)(iii)(1)(A) is C₃₆ dimer acid. .Iaddend. .Iadd.69. Thecomposition of claim 14 wherein the long-chain carboxylic acid ofcomponent (a)(i)(1) and of component (a)(iii)(1)(A) is C₃₆ dimer acid..Iaddend. .Iadd.70. The composition of claim 67, 68, or 69 wherein theshort-chain dicarboxylic acid of component (a)(i)(1) is isophthalicacid. .Iaddend. .Iadd.71. The composition of claim 67, 68, or 69 whereinthe short-chain dicarboxylic acid of component (a) (iii)(1)(A) isisophthalic acid. .Iaddend. .Iadd.72. The composition of claim 67, 68 or69 wherein the short-chain dicarboxylic acid of component (a)(i)(1) andof component (a)(iii)(1)(A) is isophthalic acid. .Iaddend. .Iadd.73. Thecomposition of claim 14 wherein the alcohol containing compound ofcomponent (a)(iii)(1)(B) is an aliphatic diol. .Iaddend. .Iadd.74. Thecomposition according to claim 20 wherein said long-chain carboxylicacid of component (a)(iii)(1)(A) is C₃₆ dimer acid. .Iaddend. .Iadd.75.The composition of claim 20 wherein the long-chain carboxylic acid ofcomponents (a)(i)(1) and (a)(iii)(1)(A) is C₃₆ dimer acid. .Iaddend..Iadd.76. The composition according to claim 21, 74 or 75 wherein saidshort-chain dicarboxylic acid of component (a)(iii)(1)(A) is selectedfrom adipic acid and isophthalic acid. .Iaddend. .Iadd.77. Thecomposition according to claim 21, 74 or 75 wherein said short-chaindicarboxylic acid of components (a)(i)(1) and (a)(iii)(1)(A) is selectedfrom adipic acid isophthalic acid. .Iaddend. .Iadd.78. The compositionof claim 24 further comprising a rheology control agent. .Iaddend..Iadd.79. The method of claim 27 wherein said long-chain carboxylic acidof component (a)(iv)(1)(A) is C₃₆ dimer acid. .Iaddend. .Iadd.80. Themethod of claim 27 wherein the long-chain carboxylic acid of components(a)(i)(1) and (a)(iv)(1)(A) is C₃₆ dimer acid. .Iaddend. .Iadd.81. Themethod of claim 28, 79 or 80 wherein said short-chain dicarboxylic acidof component (a)(iv)(1)(A) is isophthalic acid. .Iaddend. .Iadd.82. Themethod of claim 28, 79 or 80 wherein the short-chain dicarboxylic acidof components (a)(i)(1) and (a)(iv)(1)(A) is isophthalic acid. .Iaddend..Iadd.83. The method according to claim 81 wherein the alcohol having atleast 2 hydroxyl groups is 1,6-hexanediol. .Iaddend. .Iadd.84. Themethod according to claim 82 wherein the alcohol having at least 2hydroxyl groups is 1,6-hexanediol. .Iaddend. .Iadd.85. The compositionaccording to claim 31 wherein said long-chain carboxylic acid ofcomponent (d)(i) is C₃₆ dimer acid. .Iaddend. .Iadd.86. The compositionaccording to claim 31 wherein said long-chain carboxylic acid ofcomponents (a)(i)(1) and (d)(i) is C₃₆ dimer acid. .Iaddend. .Iadd.87.The composition according to claim 21 wherein the pigment particles arein the form of a premixed slurry. .Iaddend. .Iadd.88. The method ofclaim 27 wherein the at least one layer of a waterborne basecoatcomposition is further comprised of a first layer and at least one otherlayer. .Iaddend. .Iadd.89. The method of claim 88 wherein the firstlayer of the at least one layer of a waterborne coating compositionfurther comprises aluminum, mica or a mixture thereof. .Iaddend.